At the age of 7, Jonkerman started goalkeeping at VV De Meern. The club from the village where he grew up. Three years later he received offers from FC Den Bosch, PSV and RKC Waalwijk. Jonkerman opted for the latter club on the advice of his father. “He said you had better start low and work yourself up. In retrospect I regret that a bit,” says Jonkerman.